In the prior art, it is known to produce laminated roofing shingles. Most particularly, it is known to produce laminated roofing shingles wherein the shingles are comprised of a fiber sheet or mat that is impregnated with a bituminous material, such as asphalt, and with granules applied on a surface of the shingles that are to be weather-exposed in the installed condition, and with generally smaller particles such as mica, sand or the like applied to the rear of the shingles, to prevent multiple shingles in a given stack or package from adhering to each other.
It is also known in the roofing art that laminated shingles may be made by cutting shingle material of the type described above, to have tabs, with spaces between the tabs, and wherein strips of additional shingle material are applied to the posterior surfaces of the shingle material having tabs thereon, to underlie the spaces between adjacent tabs. Generally such posterior-applied shingle material is of a shorter dimension than the anterior shingle layer, in that it need not extend from the lower ends of the tabs, up to the upper end of the headlap portion, although, such a full height posterior layer can be provided, if desired.
It is generally recognized that it is more economical to provide a posterior layer of shingle material that is slightly more than half the height of the anterior layer of shingle material, so that it extends from the lower ends of the tabs of the anterior layer, to just above the upper ends of the slots or cutouts, so that the slots between adjacent tabs are fully covered.
It has been recognized that highly desirable, aesthetic effects can be obtained by using an anterior layer of shingle material that has wide slots between adjacent tabs. Such an aesthetic effect is known as a “dragon's tooth” effect.
Examples of a dragon's tooth effect exist in U.S. Pat. Nos. 6,044,608; 6,355,132 and U.S. Pat. No. 7,607,275, the complete disclosures of which are herein incorporated by reference.
It has been found that, when dragon's tooth type laminated shingles are laid up on a roof, if the shingles were produced on a production line with a continuous and repeating pattern cut into the shingle material by means of a pattern of blades on the circumference of a cutting cylinder, thereafter, when the shingles thus manufactured are laid up in courses on a roof, there may appear a pattern to the thus laid-up shingles that may not be desirable, such as, the appearance of the dragon's teeth in a generally straight line, often appearing as a sloped line of teeth, when the roof with shingles thus applied is viewed from ground level.